The invention relates to an electrical machine having a stator which has thirty six slots and thirty six teeth in an alternating sequence, as well as a winding system which is at least partially arranged in the slots and has three winding phases.
At the moment, two different embodiments essentially exist for an electrical machine such as this which, in particular, is in the form of a synchronous machine with permanent-magnet excitation, and these embodiments differ from one another in the configuration of their respective winding system.
In the first embodiment, the winding elements of the three winding phases are completely interleaved in one another. For example, that is to say, three successive slots are filled with electrical conductors which in each case belong to another of the three winding phases. In a corresponding manner, in the case of an embodiment with twelve slots, the first winding element of the first winding phase would run in the first and the fourth slots, the first winding element of the second winding phase would run in the second and the fifth slots, and the first winding element of the third winding phase would run in the third and the sixth slots. The slot occupancy of the second winding elements, which are connected in series with the respective first winding elements, result from those of the first winding elements by addition of six slot positions in each case. This winding system has four poles, that is to say two useful pole pairs, so that the ratio of the number of slots (=12) to the number of poles (=4) assumes the value 3. This is a typical minimum value for first embodiments. In an alternative first embodiment, forty eight slots are provided and sixteen poles, once again resulting in a ratio value of 3.
In the second embodiment, the winding elements of the three winding phases—apart from circuitry in the area of the end windings—are completely separated from one another. So-called tooth-wound coils are used as winding elements and, in particular, are each inserted into two adjacent slots and surround the tooth located between the two adjacent slots. In this case, electrical conductors on two different tooth-wound coils may be arranged in one slot. In a corresponding manner, in the case of a configuration with six slots, the first tooth-wound coil of the first winding phase would run in the first and the second slots, the first tooth-wound coil of the second winding phase would run in the second and the third slots, and the first tooth-wound coil of the third winding phase would run in the third and fourth slots. The slot occupancy of the second tooth-wound coils connected in series with respect to the respective first tooth-wound coil results from that of the first tooth-wound coils by addition of three slot positions in each case. This winding system also has a total of four poles, so that the ratio of the number of slots (=6) to the number of poles (=4) assumes the value 1.5. This is a typical maximum value for second embodiments. In an alternative second embodiment, the number of slots provided is twenty four, and the number of poles is sixteen, once again resulting in a ratio value of 1.5.
An electrical machine according to the first embodiment has a relatively large end winding area, whereas, in contrast, the second embodiment leads to a comparatively small overall slot area.
The object of the invention is therefore to specify an electrical machine of the type referred to initially whose response is better than that of the known prior art.